Scientists develop light-activated muscle for robots

Animals have long been a source of inspiration to researchers -- from swimming like dolphins, scurrying across walls like lizards or jumping like fleas. However, a team of researchers have now gone a step further -- using biological ingredients to build muscle cells for advanced robots to make them more 'organic'.

Scientists at MIT and the University of Pennsylvania have engineered muscle cells which can flex in response to light. Using this "bio-integrated" approach, the teams are building the light-sensitive tissue so robots could potentially become as flexible and strong as living counterparts.

The research will be published in a future issue of journal Lab on a Chip.

The team chose skeletal muscle for their robotic design, which is more powerful and stronger than cardiac muscle. Normally, neurons send electrical impulses which cause muscle to contract -- so to mimic this biological function, the Ford Professor of Engineering in MIT's Department of Mechanical Engineering and team leader Harry Asada went to the field of optogenetics.

Invented in 2005, field researchers use genetically modified neurons to respond to pulses caused by lasers and light sources. Asada's team used the technique to make skeletal muscle cells twitch -- modifying cells to contain a light-activated protein which were then fused into 3D, long muscle fibers. Afterwards, 20-millisecond pulses of blue light were beamed onto the cells.

The team found that by shining the blue light, individual fibers responded in the same manner as standard muscle -- by bending and twisting when exposed to the external stimuli -- instead of organic electrical impulses.

The researchers believe that the project has begun testing the boundaries between the organic and mechanical. Asada said:

"With bio-inspired designs, biology is a metaphor, and robotics is the tool to make it happen. With bio-integrated designs, biology provides the materials, not just the metaphor. This is a new direction we're pushing in biorobotics."

The strength of the muscle was tested through a small micromechanical chip. The muscle strips were tied to different posts, and calculated against the stiffness of the post, the muscle's force was analyzed.

Currently, the light-sensitive muscle tissue is able to expand and contract to ten degrees of freedom in space less than one millimeter wide.

The research may have a number of applications in robotics, medical devices, navigation and transport -- for example, allowing for more flexible robotic designs that move organically. One potential robotic device could be used for endoscopy -- where a camera is used within the body to investigate medical problems.

In addition, the muscle could be used to study muscle contractions when exposed to various drugs.